PROCESS FOR PREPARATION OF REDUCED METAL TITANIUM COMPLEXES

Abstract: A process for preparing titanium or zirconium hydrocarbyloxide complexes in a reduced oxidation state comprising contacting the corresponding complex in an elevated oxidation state with lithium alkyl reducing agent and recovering the resulting product.

Description: PROCESS FOR PREPARATION OF REDUCED METAL TITANIUM COMPLEXES The present invention relates to a process for preparing titanium or zirconium metal complexes in a reduced oxidation state More particularly, the present process relates to a process for preparing such metal complexes containing hydrocarbyloxy substituents in a high yield, facile manner The resulting metal complexes are used for polymerizing α-olefms including ethylene as well as viny dene aromatic monomers, such as styrene Generally the catalysts are activated for use by an activating cocatalyst such as an alkylaluminoxane or a cation forming compound Such polymers may be usefully employed in the preparation of solid objects and articles such as a moldings, films, sheets and foamed objects by molding, casting or the like process In J Am Chem Soc , 3, 581 (1961) the preparation of cyclopentadienyltitanium dichloπde by the reaction of dnsobutyl aluminum chloride with biscyclopentadienyl titanium dichlonde is disclosed In Gmehn Handbuch der Anorqanischen Chemie, Spπnger-Verlag, p 134, (1977), cyclopentadienyl titanium dihalides were stated to be prepared by reduction of the corresponding trihaiide complexes using powdered zinc reducing agent in dry, oxygen free tetrahydrofuran According to the present invention there is now provided a process for preparing titanium or zirconium metal complexes corresponding to the formula CpmMX n X'p wherein Cp is a single η 5 -cyclopentadιenyl or η 5 -substιtuted cyclopentadienyl group, the substituted cyclopentadienyl group being optionally also bonded to M through a substituent X as described hereinafter, M is titanium or zirconium in the +3 oxidation state, X each occurrence is an inert anionic hgand of upto 20 nonhydrogen atoms and optionally one X and Cp are joined together forming the divalent ligand -CpX-, X' is an inert, neutral donor ligand, n is an integer greater than or equal to 1 , p is independently O or 1 , and the sum of m and n is equal to 3, the steps of the process comprising contacting a metal complex corresponding to the formula Cp m M'X" n + 7 X'p wherein Cp, X', m, n and p are as previously defined, M' is titanium or zirconium in the +4 oxidation state, X" each occurrence is an inert anionic ligand of up to 20 nonhydrogen atoms with the proviso that in at least one occurrence X" is OR wherein R ιs Cι-10 hydrocarbyl, and optionally one X" and Cp are joined together forming the divalent -CpX"-, with a lithium alkyl reducing agent and recovering the resulting product All reference to the Periodic Table of the Elements herein shall refer to the Periodic Table of the Elements, published and copyrighted by CRC Press, Inc , 1989 Also, any reference to a Group or Series shall be to the Group or Series as reflected in this Periodic Table of the Elements, utilizing the lUPAC system for numbering groups As used herein, the term "syndiotactic" refers to polymers having a stereoregular o structure of greater than 50 percent syndiotactic of a racemic triad as determined by ,3 C nuclear magnetic resonance spectroscopy Such polymers may be usefully employed in the preparation of articles and objects via compression molding, injection molding or other suitable technique having an extremely high resistance to deformation due to the effects of temperature Illustrative but nonl i mitmg examples of X include hydrocarbyl, si lyl, halo, NR 2 , 5 PR 2 , OR, SR, and BR 2 , wherein R is as previously defined Preferably where X and R are hydrocarbyl the same are σ-bonded groups Illustrative but nonlimiting examples of X' include ROR, RSR, NR 3 , PR 3 , and C . o olefins or diolefms, wherein R is as previously defined Such donor ligands are able to form shared electron bonds but not a formal covalent bond with the metal 0 Monocyclopentadienyl and substituted monocyclopentadienyl groups for use according to the present invention are more specifically depicted by the formula wherein R' each occurrence is independently hydrogen, halogen, R, N-R 2l P R 2 , OR SR or BR 2 , wherein R is as previously defined, or one or two pairs of adjacent R hydrocarbyl groups 0 are joined together forming a fused ring system R" individually may be R or a divalent X group (or X" grouo depending on whether the reactant or product complex is being referred to) that is also covalently bonded to M Preferably, R' IS alkyl or haloalkyl of UD to 6 carbons Most highly preferably Cp is 5 cyclopentadienyl or pentamethylcyclopentadienyl Illustrative, but not limiting examples of metal complexes which may be used in the preparation of tne compounds of this invention are derivatives of titanium or zirconium Titanium is the preferred metal In a highly preferred process the complex is formed by reaction of cyclopentadienyl titanium Cj. 4 trιalkoxιdes or pentamethyltitanium C;_ 4 tπalkoxides with the reducing agent In a most highly preferred embodiment of the invention, Cp in the final product is η 5 -cyclopentadιenyl or ηS-pentamethylcyclopentadienyl, m is one, M is titanium, n is two, p is zero, X each occurrence is OR, and R is C 1 - 4 alkyl Suitable lithium alkyl reducing agents especially include Cτ- 4 alkyl lithium compounds with n-butyl lithium, sec-butyl lithium and t-butyl lithium being preferred A most highly preferred lithium alkyl reducing agent is t-butyl lithium The amount of lithium alkyl compound used preferably varies from 0 9 to 2 0 moles per mole of starting complex, and most preferably is from 1 O to 1 5 moles per mole of starting complex Recovery of the resulting complex is accomplished according to any known technique, usually by devolati zation, extraction or precipitation upon addition of a poor sol ent Preferably a quenching agent such as a ^-4 tπalkylchlorosilane, especially tπmethylchlorosilane is added to the reaction mixture to react with unreacted lithium alkyl reducing agent or lithium alkoxide by-products The amount of quenching agent used preferably varies from 0 9 to 2 0 moles per mole of starting complex, and most preferably is from 1 0 to 1 5 moles per mole of starting complex The species formed upon addition of the quenching agent are generally volatile and may be removed from the solution by heating The desired metal complexes are then removed by extraction in a hydrocarbon solvent such as hexane or a mixture of alkanes The complexes can be prepared in a suitable solvent at a temperature within the range from about -100°C to about 300°C The reactants and products are generally sensitive to both moisture and oxygen and should be handled and transferred in an inert atmosphere such as nitrogen, argon or helium Suitable solvents or diluents for the complex preparation include any of the solvents known in the prior art for metal complex formation including straight and branched-cham hydrocarbons such as $ 12 alkanes, especially, hexane, heptane, or octane, β 1 2 cyclic and a cyclic hydrocarbons such as cyclohexane, cycloheptane, methylcyclohexane and methylcycloheptane, Cβ ?2 aromatic and alkyl-substituted aromatic compounds such as benzene, toluene, xylene and decalin, inert aliphatic ethers, such as tetrahydrofuran, dimethyl ether and diethyl ether, and mixtures of the foregoing The resulting reduced metal complexes may exist in dimeπc form or as coordinated adducts with neutral Lewis bases The complexes are used in polymerization reactions according to well known Ziegler-Natta reaction conditions Typical polymerization conditions include slurry, bulk or suspension polymerizations using temperatures of from 0°C to 160°C Typical reaction times are from one minute to 100 hours, preferably from 1 to 10 hours An inert diluent or solvent may be used if desired Examples of suitable diluents or solvents include β 2 0 aliphatic, cycloaliphatic, aromatic and halogenated aliphatic or aromatic hydrocarbons, as well as mixtures thereof Preferred diluents comprise the β 1 0 alkanes, toluene and mixtures thereof A particularly desirable diluent for the polymerization is iso- octene, iso-nonane or blends thereof such as Isopar-E ® , available from Exxon Chemical Company Suitable amounts of solvent are employed to provide a monomer concentration from 5 percent to 100 percent by weight As in other similar polymerizations, it is highly desirable that the monomers and sol ents employed be of sufficiently high purity that catalyst deactivation does not occur Any suitable technique for monomer purification such as devolati zation at reduced pressures, contacting with molecular sieves or high surface area alumina or deaeration may be employed Having described the invention, the following examples are provided as further illustrative and are not to be construed as limiting Unless stated to the contrary, all parts and percentages are based on weight Example 1 All reactions and manipulations were carried out under inert atmosphere in a dry box Hexane solvent was purified by degassing, sparging with nitrogen and passing through activated alumina prior to use A 100 mL Schlenk flask was charged with 1 05 g (3 8 mmol) of pentamethylcy lopentadienyl titanium tπmethoxide (Cp * Tι(OCH 3 ) 3 ) and 35 mL of tetrahydrofuran (THF) The flask was placed in a dry ice/isopropanol slush bath (-78°C) 2 4 mL of a 1 7 M THF solution of t-butyllithium (4 mmol) was added by syringe The resulting solution was stirred for one hour Via a cannula, a solution of 0 5 g (4 6 mmol) of trimethylchlorosilane in 15 mL of THF was added dropwise with stirring Over a 14 hour period, the resulting solution was allowed to slowly warm to room temperature with stirring The volatiles were removed under reduced pressure The resulting solid was extracted with hexane, the solution was filtered and the product recrystallized at -10°C The product was a red crystalline solid, identified by i H NMR and x-ray crystal structure analysis as the dimeπc form of pentamethylcyclopentadienyl titanium (III) dimethoxide Polymerization A catalyst solution was prepared in a volumetric flask using toluene solvent The required amount of pentamethylcyclopentadienyltitanium (III) dimethoxide (Cp*Tι(OCH 3 ) ) was weighed and added to the flask and toluene added to form a 0 01 molar solution Polymerizations were carried out in a septum capped, crimp sealed ampoule The ampoule was charged with 10 ml of styrene and 75 μl of a 1M solution polymethylaluminoxane (PMA) cocatalyst in toluene The catalyst solution (37 μl) was added and the ampoule was then sealed and equilibrated at 70°C in a water bath The polymerization was quenched by the addition of methanol after one hour polymerization time The polymer sample was isolated and the solvent evaporated Percent conversion was 63 percent The polymer had a melting point in excess of 260°C consistent with a syndiotacticity of greater than 50 percent based on a racemic triad

Claims: WHAT IS CLAIMED IS: 1. A process for preparing titanium or zirconium metal complexes corresponding to the formula: Cp m MX n X'p wherein : Cp is a single η 5 -cyclopentadienyl or η 5 -substituted cyclopentadienyl group, the substituted cyclopentadienyl group being optionally also bonded to M through a substituent X; M is titanium or zirconium in the + 3 oxidation state; X each occurrence is an inert anionic ligand of up to 20 nonhydrogen atoms and optionally one X and Cp are joined together forming the divalent ligand -CpX-; X is an inert, neutral donor ligand; m is O, 1 or 2; n is an integer greater than or equal to 1 ; p is independently 0 or 1 ; and the sum of m and n is equal to 3, the steps of the process comprising contacting a metal complex corresponding to the formula: Cp m M'X" n + ,X'p wherein: Cp, X', m, n and p are as previously defined; M' istitanium or zirconium in the + 4 oxidation state; X" each occurrence is an inert anionic ligand of up to 20 nonhydrogen atoms with the proviso that in at least one occurrence X" is OR wherein R is 1 - 1 0 hydrocarbyl, and optionally one X" and Cp are joined together forming the divalent ligand -CpX"-; with a lithium alkyl reducing agent and recovering the resulting product. 2. The process according to claim 1 wherein M is titanium. 3. The process according to claim 1 wherein Cp is cyclopentadienyl or pentamethylcyclopentadienyl. 4. The process according to claim 1 wherein the complex is recovered by quenching with a Cι- 4 trialkylchlorosilane, devolatilizing he resulting solution and extracting the desired complex. 5. The process according to claim 3 wherein the C1- 4 trialkylchlorosilane is trimethylchlorosilane. 6. The process according to claim 1 wherein the alkyllithium reducing agent is tert-butyl lithium.

Inventors: NEWMAN THOMAS H, NEWMAN, THOMAS, H.
Applicants: DOW CHEMICAL CO, THE DOW CHEMICAL COMPANY
Application year: 1994
Main classification: C07F7
IPC codes: C07F7, C07F15, C07F17, C08F4, C08F10, C08F12